WO2013012800A2 - Dispositifs magnétoélectroniques et procédés de fabrication - Google Patents

Dispositifs magnétoélectroniques et procédés de fabrication Download PDF

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Publication number
WO2013012800A2
WO2013012800A2 PCT/US2012/046914 US2012046914W WO2013012800A2 WO 2013012800 A2 WO2013012800 A2 WO 2013012800A2 US 2012046914 W US2012046914 W US 2012046914W WO 2013012800 A2 WO2013012800 A2 WO 2013012800A2
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field
layer
ferromagnetic
electric
thickness
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PCT/US2012/046914
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WO2013012800A3 (fr
Inventor
Weigang Wang
Chia-Ling Chien
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The Johns Hopkins University
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
    • G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
    • G11C11/165—Auxiliary circuits
    • G11C11/1675—Writing or programming circuits or methods
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N50/00—Galvanomagnetic devices
    • H10N50/10—Magnetoresistive devices
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
    • G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
    • G11C11/161—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
    • H01L29/82—
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10B—ELECTRONIC MEMORY DEVICES
    • H10B61/00—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N50/00—Galvanomagnetic devices
    • H10N50/01—Manufacture or treatment
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N50/00—Galvanomagnetic devices
    • H10N50/80—Constructional details
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N50/00—Galvanomagnetic devices
    • H10N50/80—Constructional details
    • H10N50/85—Materials of the active region
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F10/00—Thin magnetic films, e.g. of one-domain structure
    • H01F10/32—Spin-exchange-coupled multilayers, e.g. nanostructured superlattices
    • H01F10/324—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer
    • H01F10/3286—Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy

Definitions

  • the field of the currently claimed embodiments of this invention relates to magneto-electronic devices and methods of production, and more particularly to magneto- electronic devices that include an electric-field-controllable magnetic tunnel junction and methods of production.
  • Magnetic tunnel junctions are leading devices for field sensing, nonvolatile magnetic random access memories (MRAMs) and spin logic applications 1"5 . It has been predicted that the electric field can substantially alter the interfacial magnetic anisotropy energy and even induce magnetization reversal in 3d transition ferromagnets (FMs) 6"10 , which could possibly provide a more energy efficient route to manipulate the magnetization in MTJs when compared with the spin transfer torque (STT) effect 11 . Indeed, driven by the premise that voltage-controlled switching would be far more energy saving and compatible with the
  • FePt and FePd films can be modified by up to 4% through the electric field applied at the
  • a magneto-electronic device includes a first electrode, a second electrode spaced apart from the first electrode, and an electric-field-controllable magnetic tunnel junction arranged between the first electrode and the second electrode.
  • the electric-field-controllable magnetic tunnel junction includes a first ferromagnetic layer, an insulating layer formed on the first ferromagnetic layer, and a second ferromagnetic layer formed on the insulating layer.
  • the first and second ferromagnetic layers have respective first and second magnetic anisotropies that are alignable substantially parallel to each other in a first state and substantially antiparallel in a second state of the electric-field-controllable magnetic tunnel junction.
  • a current of tunneling electrons through the insulating layer is greater in the first state than the second state, and a voltage applied between the first and second electrodes causes a change in at least one of a magnetic anisotropy energy, coercivity or domain wall velocity of at least one of the first and second ferromagnetic layers or a tunneling potential energy barrier through the insulating layer to at least assist in changing the electric-field-controllable magnetic tunnel junction from at least one of the first and second states to the other of the first and second states.
  • An electric-field-controllable magnetic tunnel junction includes a first ferromagnetic layer, an insulating layer formed on the first ferromagnetic layer, and a second ferromagnetic layer formed on the insulating layer.
  • the first and second ferromagnetic layers have respective first and second magnetic anisotropies that are alignable substantially parallel to each other in a first state and substantially antiparallel in a second state of the electric-field-controllable magnetic tunnel junction.
  • a current of tunneling electrons through the insulating layer is greater in the first state than the second state.
  • An electric field applied to the electric-field-controllable magnetic tunnel junction causes a change in at least one of a coercivity of at least one of the first and second ferromagnetic layers or a tunneling potential energy barrier through the insulating layer to at least assist in changing the electric-field-controllable magnetic tunnel junction from at least one of the first and second states to the other of the first and second states.
  • a method of producing a magneto-electronic device includes forming a first electrode on a substrate, forming a first ferromagnetic layer on the first electrode, forming an insulating layer on the first ferromagnetic layer, forming a second ferromagnetic layer on the insulating layer, and forming a second electrode on the second ferromagnetic layer.
  • the forming the insulating layer forms a layer of MgO that has a thickness of at least 1.0 nm and less than 2.0 nm.
  • the forming the first ferromagnetic layer forms a layer of Co 4 oFe 4 oB 2 o that has a thickness of at least 1.0 nm and less than 1.5 nm
  • the forming the second ferromagnetic layer forms a layer of Co 4 oFe 4 oB 2 o that has a thickness of at least 1.5 nm and less than 1.8 nm.
  • FIG. 1 is a schematic illustration of a magneto-electronic device according to an embodiment of the current invention.
  • FIGS. 2A-2C provide an example of an electric-field assisted switching in a
  • FIG. 2A (a): Schematic drawing of a p-MTJ and the effect of electric field via a small voltage supplied by a battery.
  • FIG. 2B (b): TMR curves under different bias voltages.
  • FIG. 2C (c): Dependence of the coercivities for the top and bottom CoFeB layers on electric field. Inset shows the TMR curves of an in-plane MTJ under opposite bias voltages.
  • FIG. 3 shows an example of manipulation of giant tunneling resistance by an electric field according to an embodiment of the current invention.
  • the upper panel shows response of the resistance to the applied electric field in the lower panel.
  • the schematic magnetic configuration of the top and bottom CoFeB layers is also shown.
  • the arrow represents the magnetization direction.
  • the dotted line represents the applied external magnetic field that shifts the center of the hysteresis loops.
  • the dot represents position of the magnetization on the hysteresis loop.
  • FIGS. 4A-4C provide data that illustrate effects of electric field in MTJs with different perpendicular anisotropy energy.
  • FIG. 4A (a): Dependence of TMR and zero electric field coercivity of the bottom CoFeB layer on MgO barrier thickness. Inset shows the WKB fitting of the parallel and antiparallel resistance for determining the decay rate in the MgO barriers.
  • FIG. 4B (b): Electric field dependence of the coercivity of top CoFeB layer with linear fitting for the positive field branches.
  • FIGS. 4A (a): Dependence of TMR and zero electric field coercivity of the bottom CoFeB layer on MgO barrier thickness. Inset shows the WKB fitting of the parallel and antiparallel resistance for determining the decay rate in the MgO barriers.
  • FIG. 4B (b): Electric field dependence of the coercivity of top CoFe
  • FIG. 5A-5C show an example of electric field induced unipolar switching according to an embodiment of the current invention.
  • FIG. 5A (a): Normalized minor loops of the TMR curve at different Vbias- Inset show the full TMR curve at near zero Vbias where both FM layers are switched by magnetic field. This MTJ has the structure of CoFeB(1.3 nm)/MgO (1.2 nm)/CoFeB(1.6 nm).
  • Vertical dotted line represents the position of the constant Hb ias .
  • the moment of bottom CoFeB is fixed pointing down.
  • FIG. 6 shows a representative TMR curve of the MTJs with thicker CoFeB electrodes (3nm)
  • FIG. 7 shows TMR curves of the junctions with different top CoFeB layers.
  • FIG. 8 shows AHE of Ta/CoFeB/MgO with different MgO thickness.
  • FIG. 9 shows bias dependence of TMR for the MTJ shown in Figure 2B.
  • FIGS. 10A-10B show the determination of anisotropy energy change under electric field in CoFeB/MgO/CoFeB junctions according to an embodiment of the current invention.
  • FIGS. 10A (a): Hard-axis TMR curve of a MTJ with the key structure of CoFeB(1.2 nm)/MgO(1.8 nm)/CoFeB(1.6 nm) under in plane magnetic field.
  • the inset shows the electric field dependence of saturation field by hard-axis TMR measurement (corresponding to the anisotropy field of the bottom CoFeB layer) and the He of the bottom CoFeB layer by easy- axis TMR measurement.
  • FIG. 1 provides a schematic illustration of a magneto-electronic device 100 according to an embodiment of the current invention.
  • the magneto-electronic device 100 includes a first electrode 102, a second electrode 104 spaced apart from the first electrode 102, and an electric-field-controllable magnetic tunnel junction 106 arranged between the first electrode 102 and the second electrode 104.
  • the electric-field-controllable magnetic tunnel junction 106 includes a first ferromagnetic layer 108, an insulating layer 110 formed on the first ferromagnetic layer 108, and a second ferromagnetic layer 112 formed on the insulating layer 110.
  • the first and second ferromagnetic layers (108, 112) have respective first and second magnetic anisotropies that are alignable substantially parallel to each other in a first state and substantially antiparallel in a second state of the electric-field-controllable magnetic tunnel junction 106.
  • a current of tunneling electrons through the insulating layer is greater in the first state than in the second state.
  • a voltage applied between the first and second electrodes (102, 104) causes a change in at least one of a magnetic anisotropy energy, coercivity or domain wall velocity of at least one of the first and second ferromagnetic layers (108, 112) or a tunneling potential energy barrier through the insulating layer 110 to at least assist in changing the electric-field-controllable magnetic tunnel junction from at least one of the first and second states to the other of the first and second states.
  • the second ferromagnetic layer is constructed to have a coercivity that increases with a change in the voltage applied between the first and second electrodes (102, 104) while the first ferromagnetic layer has a coercivity that decreases with the change in the voltage applied between the first and second electrodes (120, 104).
  • the coercivity of the second ferromagnetic layer 112 (top) increases while the coercivity of the first ferromagnetic layer 108 (bottom) decreases.
  • magneto-electronic device 100 can include a substructure 114, which can include a substrate 116 and other components.
  • the substructure can include a source of a bias magnetic field 118 according to some embodiments of the current invention.
  • the electric-field-controllable magnetic tunnel junction 106 is arranged in the bias magnetic field such that the second anisotropy of the second ferromagnetic layer has parallel and antiparallel orientations relative to the bias magnetic field.
  • the voltage applied between the first and second electrodes (102, 104) causes a change in a coercivity of the second ferromagnetic layer 112 to assist the bias magnetic field to change the second anisotropy of the second ferromagnetic layer 112 from the antiparallel to the parallel orientation relative to the bias magnetic field while the first magnetic anisotropy of the first ferromagnetic layer 108 remains unchanged in orientation.
  • the source of the bias magnetic field 118 provides a substantially constant magnetic field.
  • the source of the bias magnetic field 118 can be a permanent magnet, such as a layer of magnetic material.
  • the source of the bias magnetic field 118 can provide a changeable magnetic field.
  • the source of the bias magnetic field 118 can be, or include, an electromagnet in some embodiments.
  • the first and second magnetic anisotropies of the first and second ferromagnetic layers 108, 112) can be substantially perpendicular to the first and second ferromagnetic layers (108, 112), i.e., a p-MTJ.
  • the term "insulating layer”, as used herein, is intended to refer to an electrical insulator.
  • the insulating layer 110 provides a tunneling potentially energy barrier in which electrons pass through by quantum mechanical tunneling to provide a tunneling current.
  • the structure and composition of the tunneling barrier has a large effect of the probability of electron tunneling through the barrier.
  • the insulating layer 110 can be a MgO layer.
  • the insulating layer 110 may consist essentially of MgO.
  • the insulating layer 110 can consist essentially of MgO, AIO, Hf0 2 , Ta 2 C"5, or ZrO, or any combination thereof.
  • Co 4 oFe 4 oB 2 o has been found to be a suitable material for the ferromagnetic layers 108 and 112. Although this ferromagnetic material has been found to work well for particular embodiments, the general concepts of the current invention are not limited to only the use of Co4oFe4oB 2 o.
  • the first ferromagnetic layer 108 has a thickness of at least 0.7 nm and less than 1.2 nm, and the second ferromagnetic layer 112 has a thickness of at least 1.6 nm and less than 1.7 nm. In some embodiments, the first ferromagnetic layer 108 has a thickness of at least 1.0 nm and less than 1.5 nm, and the second ferromagnetic layer has a thickness of at least 1.5 nm and less than 1.8 nm. In some embodiments, the MgO insulating layer has a thickness of at least 1.0 nm and less than 2.0 nm.
  • the MgO insulating layer has a thickness of about 1.4 nm.
  • the term "about” as used in this case means that the thickness is less than 1.5 nm, but more than 1.3 nm. However, in some embodiments, it can be closer to 1.4 nm.
  • magneto-electronic device 100 can include a plurality of electric-field-controllable magnetic tunnel junctions arranged between respective pairs of electrodes (only one illustrated in Figure 1) such that the magneto-electronic device 100 is a non- volatile data storage device.
  • the magneto-electronic device 100 can be a write-once data storage device in some embodiments, or can be a rewritable data storage device in other embodiments.
  • the magneto-electronic device 100 can rely on either constant or re- orientable bias magnetic fields in combination with applied voltages to write and/or erase data when the magneto-electronic device 100 is a data storage device.
  • an applied current in combination with applied voltages can also be used to write and/or erase data in data storage devices according to some embodiments of the current invention.
  • the magneto-electronic device 100 is not limited to only data storage devices.
  • a method of producing a magneto-electronic device includes forming a first electrode on a substrate, forming a first ferromagnetic layer on the first electrode, forming an insulating layer on the first ferromagnetic layer, forming a second ferromagnetic layer on the insulating layer, and forming a second electrode on the second ferromagnetic layer.
  • the insulating layer is formed as a layer of MgO that has a thickness of at least 1.0 nm and less than 2.0 nm.
  • the first ferromagnetic layer is formed as a layer of Co 4 oFe 4 oB 2 o that has a thickness of at least 1.0 nm and less than 1.5 nm.
  • the second ferromagnetic layer is formed as a layer of Co 4 oFe 4 oB 2 o that has a thickness of at least 1.5 nm and less than 1.8 nm.
  • the first ferromagnetic layer is a layer of Co 4 oFe 4 oB 2 o that has a thickness of at least 0.7 nm and less than 1.2 nm
  • the second ferromagnetic layer is a layer of Co 4 oFe 4 oB 2 o that has a thickness of at least 1.6 nm and less than 1.7 nm.
  • the insulating layer is a layer of MgO that has a thickness of about 1.4 nm.
  • the MTJs based on MgO tunnel barrier are the devices of choice for read heads, MRAM and logic elements. Usually, the MTJs have relatively thick FM layers
  • the structure of the MTJs is Si/Si0 2 /Ta(7nm)/Ru(15nm)/Ta(7nm)/
  • Co 4 oFe 4 oB 20 (l .2-1.3nm)/MgO(l .2-2nm)/Co 4 oFe 40 B 2 o(l .6 nm)/Ta(10nm)/Ru(24nm), where the most essential part is CoFeB/MgO/CoFeB with a schematic shown in Figure 2A.
  • the films were deposited in a multi-source UHV magnetron sputtering system with the base vacuum of 3 x 10 ⁇ 9 Torr. After the deposition of the multilayers, MTJs in circular shapes with radius (r) ranging from 200nm to 25 ⁇ were fabricated and measured by 4-probe method on a probe station at room temperature (see below).
  • the positive bias voltage corresponds to tunneling of electrons from the bottom CoFeB electrode to the top CoFeB electrode.
  • the highest TMR ratio reached is 118%, close to the maximal reported TMR of 124% in this system 5 .
  • FIG. 2B The striking effect of the electric field via a bias voltage Vbias on magnetic anisotropy in these p-MTJs is presented in Figure 2B.
  • the low and high resistance states are those with parallel (P) and antiparallel (AP) magnetizations with the switching fields at the coercivities of the two FM electrodes.
  • the bias dependence of the TMR shows a normal behavior (see below).
  • the switching characteristics of the MTJ depend explicitly on the bias voltage Vuas, its value as well as its sign. Since the observed phenomenon is parity-odd with respect to the applied voltage, the possibility of heating effects can be ruled out.
  • the in-plane MTJs exhibit zero-bias TMR ratio between 200-350% but with no discernable difference between ⁇ Vu as , as shown in the insert of Figure 2C, where the switching field at 770 mV and -770 mV are virtually the same as one would expect.
  • This demonstrates that the strong electric field effect only exists in MTJs with interfacial magnetic anisotropy. It may be noted that in the previous studies using single FM layers 24 ' 26 , a large voltage of 200 V was needed to observe appreciable electric field effects.
  • FeCo/MgO/Fe junctions the modification of magnetic anisotropy could only be indirectly probed by STT induced
  • a voltage pulse of - 400 mV (corresponding to an electric field of - 0.24 V/nm) was then applied to the MTJ. Due to the decreased He, the magnetization of the top layer is reversed by this -400 mV pulse since now the only possible magnetic state is pointing down under Hbias- The bottom CoFeB electrode is left intact due to its larger, and in fact increased, He. This is evidenced by the larger junction resistance of about 4200 ⁇ in the antiparallel (AP) state as a result of the -400 mV pulse, and remains so after the -400 mV pulse was removed.
  • AP antiparallel
  • the easy-axis He of the bottom CoFeB layer increases from 40 Oe to 150 Oe when MgO thickness has been reduced from 1.8 nm to 1.2 nm, while maintaining TMR very close to 100%.
  • the WKB fitting shown in the inset of Figure 4 A yields a decay rate constant of 8.3 nm "1 , very close to 8.6 nm "1 obtained previously from in- plane junctions fabricated under similar condition 34 , indicating that all the MgO tunnel barriers at different thickness behave normally in these p-MTJs.
  • the nearly constant TMR is a reflection that the TMR reduction due to the slight overoxidation at a thicker MgO barrier is compensated by the natural increase of TMR with MgO thickness 4 ' 35 .
  • the PMA depends sensitively on the oxidation states because it is originated from the hybridization of the 3d orbitals of transition metals and the 2p orbitals of oxygen from MgO 36 ' 37 .
  • Figure 3 will require changing the direction of Hbias-
  • a special unipolar switching process to reversibly control the resistance states under a constant Hbias-
  • the STT effect occurring in MTJs with submicron sizes is greatly facilitated by the reduced PMA at negative voltages, which can be used to complement the electric field to achieve reversible switching.
  • the minor loops of the TMR curve are shown in Figure 5 A, with the zero-voltage full TMR curve shown in the inset.
  • the He of the top CoFeB again shows dramatic change under different bias voltages.
  • the He is 70 Oe at near zero bias.
  • the STT switching occurs at the current density of -1.2 x 10 4 A/cm 2 (-15 ⁇ ), thanks to the greatly reduced energy barrier and the applied Hbias favoring AP state, which is much smaller than the normal STT switching current density at ⁇ 10 6 A/cm 2 . Therefore the magnetization is very efficiently brought to the up direction by Vi and stays pointing up after Vi is removed. The switching back is achieved by applying a more negative voltage V 2 . Now the loop becomes the one in black color because
  • the current corresponding to V 2 is -45 ⁇ , therefore the average switching current density is only -2.4 x
  • the activation energy is determined to be 42 ksT by the change of He under different magnetic field ramp rates, indicating the magnetization reversal is through the incoherent mode, as suggested in previous studies 5 ' 39. Heating is always a concern during the STT switching.
  • the fact that the He at +870 mV is more than 20 times larger than the He at -870 mV suggests that this greatly reduced switching current is primarily due to the effect of electric field.
  • the usual spin torque switching by positive pulses can never change the resistance state for the case here due to the enhanced energy barrier under positive electric field. Indeed, attempting switching from AP to P state with positive pulses leads to the breakdown of the MTJ at about +2V.
  • the MTJs in the above examples were fabricated using a 10-source UHV magnetron sputtering system.
  • the structure of the MTJs in this study is Si/ Si0 2 /Ta(7nm)/Ru(15nm)/Ta(7nm)/Co 4 oFe 4 oB 2 o(l .2-1.3 nm)/MgO(l .2-
  • the base pressure of the sputtering chamber is 3 x 10 ⁇ 9 Torr. All the metal layers were deposited by DC sputtering under a pressure of 2 mTorr. The MgO layer was deposited by RF sputtering under a pressure of 1 mTorr. The deposition rate of MgO layer is about 0.25 A/s.
  • H 2 and H 2 0 partial pressure in the chamber was closely monitored by a residue gas analyzer.
  • the H 2 0 partial pressure was substantially reduced by pre-sputtering Ta prior to the MgO layer disposition (Nagamine, Y. et al. Ultralow resistance-area product of 0.4 Omega(mu m)[sup 2] and high magnetoresistance above 50% in CoFeB/MgO/CoFeB magnetic tunnel junctions.
  • Circular MTJs with radius ranging from 200nm to 25 ⁇ were fabricated after the disposition of multilayers.
  • the fully patterned MTJs were then annealed for 5-30min in a rapid thermal annealing system in Ar atmosphere under the perpendicular field of 3 kOe (Wang, W. G. et al. Understanding tunneling magnetoresistance during thermal annealing in MgO-based junctions with CoFeB electrodes.
  • the sample structure is Si/Si0 2 /Ta(7nm)/Ru(15nm)/Ta(7nm)/Co4oFe4oB 2 o(l .2nm)/MgO(l .5nm)/Co 4 oFe4oB 2 o(l .5- 2nm)/Ta(10nm)/Ru(24nm).
  • the threshold for the perpendicular magnetic anisotropy for the top CoFeB layer is about 1.8nm.
  • the switching of the hard layer occurs at approximately 450 Oe.
  • the switching of the soft layer shows obvious difference. Since the only difference in these samples is the thickness of top CoFeB electrode, we can identify the bottom CoFeB as the hard layer with the larger switching field and the top CoFeB layer as the soft layer with smaller switching field.
  • the evolution of the switching field for the top electrode is due the change from perpendicular to in plane magnetic anisotropy when the thickness of top CoFeB increases.
  • the bias dependence of TMR for the p-MTJ has the expected behavior of decreasing TMR with increasing V as, with a half voltage (at which TMR drops to half of its zero-bias value) about 370 mV as shown in Figure 9.
  • the bias dependence of TMR for the MTJ in Figure 5 shows very similar behavior.
  • samples with the structure of Ta(7nm)/MgO(1.2 nm)/CoFeB(1.6 nm)/Ta (5nm) were tested.
  • the saturated magnetization was found to decrease to be about 500 emu/cm , possibly due to magnetic dead layer in this structure (Ikeda, S. et al. A perpendicular-anisotropy CoFeB- MgO magnetic tunnel junction. Nature Materials 9, 721-724 (2010)).
  • CoFeB(1.2 nm)/MgO(1.8 nm)/CoFeB(1.6 nm) is shown in Figure 10A.
  • the magnetoresistance of this junction also saturates at 1700 Oe.
  • the saturation field of the TMR curve under in plane field corresponds to the anisotropy field of the bottom CoFeB.
  • the anisotropy field of the bottom CoFeB varies quasi linearly with the electric field as shown in the inset of Figure 4B.

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Abstract

L'invention porte sur un dispositif magnétoélectronique qui comprend une première électrode, une seconde électrode espacée de la première électrode, et une jonction tunnel magnétique pouvant être commandée par champ électrique agencée entre la première électrode et la seconde électrode. La jonction tunnel magnétique pouvant être commandée par champ électrique comprend une première couche ferromagnétique, une couche isolante formée sur la première couche ferromagnétique, et une seconde couche ferromagnétique formée sur la couche isolante. Les première et seconde couches ferromagnétiques possèdent des première et seconde anisotropies magnétiques respectives qui peuvent être alignées sensiblement parallèles l'une à l'autre dans un premier état et sensiblement antiparallèles dans un second état de la jonction tunnel magnétique pouvant être commandée par champ électrique. Un courant d'électrons par effet tunnel à travers la couche isolante est plus fort dans le premier état que dans le second état, et une tension appliquée entre les première et seconde électrodes provoque une modification dans une énergie d'anisotropie magnétique, champ coercitif ou vitesse de paroi de domaine d'au moins une des première et seconde couches ferromagnétiques, et/ou dans une barrière tunnel d'énergie potentielle à travers la couche isolante pour au moins aider à faire passer la jonction tunnel magnétique pouvant être commandée par champ électrique d'au moins un des premier et second états à l'autre des premier et second états.
PCT/US2012/046914 2011-07-15 2012-07-16 Dispositifs magnétoélectroniques et procédés de fabrication WO2013012800A2 (fr)

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US9853053B2 (en) 2012-09-10 2017-12-26 3B Technologies, Inc. Three dimension integrated circuits employing thin film transistors
US8988923B2 (en) * 2012-09-11 2015-03-24 The Regents Of The University Of California Nonvolatile magneto-electric random access memory circuit with burst writing and back-to-back reads
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